Multi-element radio frequency (RF) coil systems are becoming a central component of high field magnetic resonance (MR) systems in order to reduce SAR and to improve B1-homogeneity. Also at lower field strength local parallel transceiver (TX) systems are gaining significant interest since they have the potential to reduce system cost.
Especially in MR coil systems with a plurality of coil elements supplied by one RF signal source there are obvious developments to use more coil elements than transmit channels of the system. This means, that several coil elements are fed simultaneously by one transmit channel via a feeding circuit arrangement comprising a power divider (splitter, hybrid coupler, . . . —with or without phase shifters) and a plurality of feeding lines. In this way fixed amplitude and phase relationships between the coil elements of one TX channel can be set. The principle can also be used in single TX channel systems (like 1.5 Tesla systems) to feed TX coil arrays.
Patent specification U.S. Pat. No. 7,633,293 B2 shows a very complex parallel transceiver system with a RF signal source, a magnetic resonance coil system with a plurality of coil elements and a feeding circuit comprising a plurality of feeding lines, wherein each feeding line for feeding a corresponding coil element comprises a high-power amplifier and a transmit-receive switching device for each coil element. The transmit-receive switching devices operate to switch between transmission and receiving circuits for each of the coil elements.